This invention relates to a marine engine and drive unit having a superior configuration including low profile, aftwardly extending center of gravity and improved silencing, and enabling the trimming adjustment of the drive unit with minimum forward displacement of the center of gravity from its aft position to improve trim.
Conventional outboard motors have a generally linear orientation due to the direct connection of the crankshaft and driveshaft. The pistons of a conventional outboard motor are typically horizontally displaced about a vertically oriented crankshaft. This linear drive orientation causes the center of gravity of the conventional outboard motor to be located relatively high and relatively close to the transom of the boat onto which it is attached.
In addition, and particularly due to the shorter configuration resulting from a linear drive arrangement, a relatively short exhaust path present in conventional outboard motors increases the noisiness of the engine and does not permit optimum tuning for the best performance. This is particularly true in the case of a two cycle engine.
In conventional units, since the points of attachment of the outboard motor to the boat is primarily aft of the transom, the conventional outboard motor has to be more limited in its range of movement to accommodate space restrictions which may be encountered for different types of boats. Conversely, boats utilizing conventional outboard motors must have large motor wells to accommodate an array of different outboard motors, each having an intrusive tilt characteristic.
One way to mitigate the unwanted attributes described above is with a configuration known as an inboard/outdrive marine unit. However, the inboard/outdrive requires a hole to be cut in the transom and a special support for the engine which typically lies near the base of the hull. Such a solution is not a solution for outboard motors, but in reality an entirely different type of marine propulsion unit.